Bosch Off-Highway

Off-Highway Starter HEF 109

HEF109-L - starter motor for commercial vehicles and off-highway applications from Bosch


Large-volume engines place great demands on starters. At the top end of the power range, Bosch offers an addition to its 24-volt starter motor portfolio: the HEF109-L “large” heavy-duty starter motor for commercial vehicles and off-highway applications. The powerful starter motor generates 18 percent more power than the tried and tested “M” (medium) type starter motor on which it is based, and thus delivers a maximum output of 9.2 kilowatts. This is enough to reliably start engines with up to 28 liters displacement.

Compact, robust, and reliable
The design of the HEF109-L with its 6-pole excitation concept is especially compact, making it particularly suitable for applications where installation space in the engine compartment is limited. The high thermal robustness ensures reliable starting of large engines – even at very low ambient temperatures or in long-lasting starting sequences.
Due to the significantly greater service-life requirements associated with commercial vehicles, the engagement itself is designed as a two-stage process in order to limit the wear of the ring gear and pinion: In the first stage, the pinion shaft including the pinion is moved forward cautiously, engaged, and turned slightly. In the second stage, the main current is released and the actual starting sequence takes place.
A mechanical relay integrated in the starter makes a connection to the engine control unit (ECU) easier. Unlike starts by ignition switch, the ECU can automatically control the starting sequence, which keeps emissions low.

For extreme conditions
The HEF109-L can also be upgraded. One example is the special dust protection, available up to IP57 protection class. An additional feature is the isolation of terminal 31. This separate connection to the batterys minus pole is a feature of special applications such as railroad vehicles or watercraft, where increased safety and protection requirements against moisture and water apply. For maximum flexibility in diverse installation conditions, the starter motor can also be supplied with all common flange geometries, including a rotatable flange.

Learn more about the HEF109

Applications of HEF109-L and advantages at a glance

For applications utilizing even larger-displacement engines and high additional hydraulic loads, Bosch offers parallel starting systems. By setting two or three starter motors of the 109-family in a parallel-system configuration, the output of each individual starter motor can be aggregated. Hence, the scope of application can be increased.

  • Powerful solution for diesel engines of up to 28 liters displacement as well as for stationary gas-powered engines
  • Engineered for mileage of up to 800,000 kilometers or 14,000 operating hours in off-highway applications
  • Adaptable to stringent system requirements
  • Application of HEF109-L
  • Application of HEF109-L
  • Application of HEF109-L